Answer number 2 and 3 please

Name one similarity and one difference between the morphology of a brachiopod and a bivalve

The fish shown above is a tarpon. it is a fast-swimming and powerful open-water fish. its closest relatives, oddly, are burrow-dwelling conger eels that stay on the bottom. both eels and tarpon developed from snake-like larvae that float in the plankton during the first stages of life. once they mature, tarpon and eels are not found near one another in the ocean. the tarpon and the eel illustrate all of the following except

What element is able to combine with itself and hydrogen to form large molecules ?